Telegraph system



J' H. BELL.

TELEGRAPH SYSTEM.

APPLICATION FILED NOV. 25, 1919.

Patented Sept. 7, 1920.

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transmitting telegraphic sign is over long JOHN H. BELL, OF SOUTHORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC P AI'ENT OFFICE.

GOIVLPANY, INCORPORATED, 9F NEW" YORK, N. "55., A CORFORATION O1? NENYORK.

TELEGRAPH SYSTEM.

Specification of Letters Eatent.

iatcnted Sept/7, 1920.

To all whom may concern:

Be it known that l, Jenn ll. BELL, a citizen of the United t ltates,residing at South Orange, in the county of Essex; State of NewJerseyhave invented certainnew and useful Improvements in TelegraphSystems, of which the following is a Tfllll, clear, con cise, and exactdescription. 7

'lhis invention relates to telegraph systems and are particularly tosvstems tor submarine cables or other conductors having highelectrostatic capacity.

its object is a transmitting system suitable for duplex working and onewhich will produce, so far as .ssible, no cnn'inlatire charging of thecable and the consequent signal distortion known as wandering zero. 7 I

ln duplex operation where the main transmission line is balanced by anartificial line it is essential that the impedance of the artificialline be made to approximate very I closely the impedance of the realline. While it is comparatively easy to obtain this bal ance for steadycurrents, it is decidedly more diiiicult to compensate for the momentaryunbalance which occurs for example when the sending voltage is suddenlyap plied to the cable for the reason that the artificial line cannot bemade an exact copy ofthe real line for these transient effects. Theresult is thataduplex jar or, in other words a momentary disturbance-ofthe local receiving relay by the locally transmitted impulses isproduced whieh'canses mutilation ol signals being received from thedistant station.

To prevent this duplex jar, it has been proposed to use sinusoidalcurrent impulses sages in the Baudot code or in similar codes over oceancables.

The invention comprises an alternatin" current generator or preferably apair or such generators which produce approximately sinusoidal waves;These generators are associated through a common driving mechanism witha transmitting distributor in such a way that the passage of tiedistributor brush over each distributor segment coincides in time withthe duration oi a. single hall. wave ol? the alternating current. Theimpulse sent to the line from any one distributor segment may be eithera positive hall wave or a. negative halt wave, depending upon theselective operation or a pair of polarized relay. associated with thealternating current source.

The specific embodiment of the invention herein disclosed pro-rides livepole-changing switches for transmitting telegraphic inipulses inaccordance with the l audot code. These pole-changing switchesiareconnected to a set of di'l'le'rential relays which cooperate with a setof segments on the distributer to determine the character of the impulseto be sent to line from the transmitting segments of the distributor.

The invention will be more clearly understood by reference to theaccompanying drawing in which Figure 1 illustrates in diagrammatic forman embodiment of the invention arranged for multiplex ope 'ation. Figs.2 and 3 represent characteristic signal combinations with thecorresponding currentimpulses necessary for their transmission, and Fig.l shows an alternative arrangement whereby a single alternating em rentgenerator may be used instead of two alternating current generators.

Referring to Fig. 1, the transmitting apparatus for one channel B of amultiplex system is shown together with portions of the adjacentmultiple): channels A and (I. A distributor X, preferably of the rotarytype, is shown in extended form and is understood to be driven bysuitable driving mechanism which also serves to drive the twoalternating current generators l and 2 and to maintain a definite fixedphase relation between the alternating current generators and thedistributer.

The alternators l and 2 are furthermore arranged to produce currentslSl) degrees other of its windings.

out of phase with each other so that a positive half cycle produced byone alternator coincides in time with a negative half cycle produced bythe other. The output of the alternators 1 and 2 is controlled bypolarized relays 3 and 41- rcspcctively, relay-3 being polarized toconnect alternator l. to the conductor 8 when a positive impulse flowsthrough conductor 5 and relay i being arranged to connect alternator 2to the con tery to the segments 11, 13' and 15, while pole changers 32and 3-1 connect positive battery to segments 12 and 14-, and that whenany of the pole changers is operated to produce a desired codecombination, the polarity applied to its corresponding distributersegment will be reversed. 'Each pole changer moreover is connected totwo of the differential relays 4:0 to 4:6, for example, pole changer 31is connected to one winding of relay 41 and one winding of relay 4L2,pole changer 32 is connected to one winding of relay I2 and one windingof relay 43, etc. Thus each of the relays e0 to 416 depends for itsoperation on the character of two adjacent impulses from the polechangers. If all of the pole changers are in the unselected position, asshown in the drawing, each of the differential relays is unenergized,for example, relay 1 receives positive current from pole changer 30through one of its windings, and negative current from pole changer 31through the Consequently this relay through its back contact connectsground to the transmitting segment 21 and will apply 2. ground to theline L through the common ring 27 when the distributor brush 19 passesover the segment 21. Similarly each of the other relays, beingunenergized, applies ground to the line through its correspondingdistributer transmittingsegments 20 to 26.,

The operation of the system may best be understood from theconsideration of a typical code combination in which the first, thirdand fourth impulses of a five impulse code are marking impulses, whilethe second an d fifth impulses are spacing impulses, and let us alsoconsider t at the last impulse sent out by the preceding channel A was aspacing impulse. The term marking impulse is here'applied to an impulsewhich is intended to perform some selecting action at segment 23 withconductor 8.

a distant station, whereas a spacing impulse is one which produces noselecting action. V a

In ordinary Baudot' operation, the marle ing impulses are ordinarilypositive impulses, while the spacing impulses are negative impulses. Theterms positive and negative are hardly applicable in the presentinstance, however, because of the particular arrangement of the polechangers and the code employed. Considering the specific codecombination above'referred to, however, the signal combination taken foran example, is shown by curve D in Fig. 2. Inasmuch as the last impulseof channel A was a spacing impulse, the pole changer 31 will be in theposition shown. The first impulse in channel B is, however, to bemarking impulse so pole changer 31 will be moved to the right and willthus connect positive battery to segment 11 and to one winding of relay11. The other winding of relay 41 will receive positive battery frompole changer 30. Consequently relay will be operated and move itsarmature to the forward contact, thus connecting seg- 'ment 21 to theconductor 8 which leads to the contacts of relays 3 and 4. Whendistributer brush 9 reaches segment 11, positive current will thereforeflow from the distributor contact 11 by way of common ring 1'7 to therelays 3 and 1. This positive impulse causes relay 3 to operate andclose its contact, thereby connecting the alternator 1 to the segment 21and inasmuch as brush 19 is now connected to se ment 21 with the commonsending ring '27, a positive half cycle of current will be sent to lineL.

The second impulse of the series being a spacing impulse, pole changer32 will not be operated but will be in the position shown. This connectspositive current to segment 12 and also to one windin of relay 412. Theother winding of relays-2 is also receiving positive current from polechanger 31, therefore relay is operated and C011 nects, through itsforward contact, segment 22 with the conductor 8. This positive cur rentagain causes the operation of relay over the conductor 5 when the brush9 reaches segment 12 and connects it to ring 17. In this second positionof the distributer the alternator 1 will send out a negative half cycleof current to'the line L. Thethird impulse being a marking impulse, polechange 33 will be moved to the rightand will thus connect positivecurrent to se ment 13 andalso one winding of relav 13. The other windingof relay 43 is alsh receiving positive current from the back contact ofpole changer 32, consequently re lay 13 is operated and connectsdistributer The positive current again causes the operation of relay 3and in this position of the distributer causes a positive half cycle ofcurrent to be sent to line L. The fourth impulse being a markingimpulse, the pole changer 34 will be moved to the right and will connectnegative battery to segment 14 and also to one winding of relay 44. Theother winding of relay is however, receiving positive current from polechanger 33, therefore relay 44 does not operate, but instead ground willbe connected to segment 24 through the back contact of relay 44. Thefifth impulse being a spacing impulse, the pole changer 35 is notoperated butjremains in the position shown and connects negative batteryto segment and also to one winding of relay The other winding of relay45 is receiving negative battery from pole changer 34,consequently relay45 operates and connects segment 25 to conductor 8. This negativecurrent also causes the operation of relay 4 when the distributer 9connects segment 15 with common ring 17 and causes a negative half cycleof current to be sent to line by way of conductor 8 and segment 25. thisis shown diagrammatically in Fig. 2, wherein the curve E representscurrent generated by alternator 1, curve F represents the currentgenerated by alternator 2, and

the shaded portions indicate the signal impulses actually sent to line.

As a second example of the operation of the system, the code combinationillustrated in curve D of Fig. 3 may be considered. In this instance thelast impulse sent out from channel A is assumed to have been a markingimpulse, while the code combination to be sent out from channel B is onein which the first, third, fourth and fifth are marking impulses and thesecond impulse is a spacing impulse. In this case pole changer will havebeen moved to the right and will connect negative battery to one windingof relay 41. Pole changer 31 will also be moved to the right and willconnect positive battery to the other winding of relay 41 and to thesegment 11. Therefore, relay 41 is not operated and the line will begrounded during the time the brush 19 is passing over the segment 21.

The second impulse being a spacing impulse, pole changer 32 remains inthe position shown and applies positive battery to one winding of relay42 and to the segment 12. The other winding of relay 42 is alsoreceiving positive current from pole changer 31, consequently the relay42 operates and when the distribnter brush 9 reaches segment 12 relay 3also operates to connect a negative half cycle of current to the line byway of distributor segment 22. v

The third impulse being a marking impulse, the pole changer 32 is movedto the right and connects positive battery to one winding of relay 43and to the distributor segment 13. The other winding of relay reachessegment 13, relay again ooerates to connect, in this ea. c, a positive h2 cycle of current to the line L through distributor segment The fourthimpulse being a marking a pulse, pole changer 34 is moved to the 1 ghtand connects negative battery to one winding of relay and also tosegment 14. The other winding of rela 44 is receiving positive batteryby way of pole changer 33, Consequently relay 44 does not operate butconnects ground'to segment 24 through its back contact.

The fifth impulsc'being a marking inipulse, pole changer is moved to theht and connects positive battery to one windof relay 45 and segment 15.The other winding of relay 45 is receivin negative battery through polechanger 44, consequently relay 45 does not operate but connects groundto the line through its back contact and segment 3-5 of the distributor.

If new the first impulse to be sent out from channel C is to be amarking impulse, the line will continue to be grounded, whereas if thisfirst impulse to be a spacing impulse, a negative half cycle of currentwill be sent to the line, as illustrated in curves E of Fig. 3.

Inspection of these curves shows that an impulse is sent to line onlywhen the permutation to be transmitted calls for a reversal in thecharacter of the impulse and that when two or more succeeding impulsesof the same character are called for in a permutation, the line will begrounded after the first of these first impulses has been transmitted.

The transmitting system above described is thus seen to send out aperfectly symmetrical series of current impulses, that is, each impulseis followed by an impulse of the same length but of opposite polarity sothat there is no opportunity for the cable to build up a cumulativecharge of either positive or negative polarity. Furthermore, thefrequent grounding of the cable insures that any accidental charge onthe cable will be drained ofi.

Owing to the fact that the impulses transmitted are sinusoidal incharacter, it is furthermore readily seen that the system is one whichis particularly well adapted to duplex operation and should produce aminimum of disturbance from duplex jar.

In the alternative arrangement shown in Fig. 4, a single alternatingcurrent generator l is used instead of the two generators 1 and 2 ofFig. 1. The two terminals of this are connected to the armature contactsof relays 3 and 4 respectively, so that each half cycle may be sent toline in one direction or the other depending on the selective operationof relays 8 and l.

hat is claimed is:

1. In a telegraph transmitting system, a set of pole changers, a sourceof alternating current, a distributor having two groups of commutatorsegments, a pair of polarized relays connected to said. source ofalternating current and selectively controlled by the cooperation ofsaid pole changers and one "of said groups of segmentsior sendlngpositive or negative hall cycles of said alternating current to linethrough said second group of segments.

2, In a telegraph transmitting system, a set of pole changers, acorresponding set oi diiierential relays, each oi? which is under thejoint control of two of said pole changers, a distributor having twogroups of commutator segments, each segment of one of said groups beingarranged to ground the line through the normally closed back con tact ona corresponding one of said relays and to send a half cycle ofalternating current to line through the front contact of said relay whenoperated, and means under the joint control oi" said pole changers andsaid other group of segments for determin ing the polarity of the halfcycle so sent.

I In a telegraph transmitting system,

a group of permutation pole changers, alternate pole changers beingnormally con nected to the positive pole of a direct our rent source,the intermediate pole changers source with said distributor.

l. In a telegraph transmitting system, a group of permutation polechangers, alternate pole changers being normally connect ed to thepositive pole of the direct current source, the intermediate polechangers be ing normally connected to the negative pole of the directcurrent source, a differential relay having two windings connected totwo adjacent pole changers respectively, and ar ranged to be operatedWhei either of said pole changers is operated individually, but

to-remain uuoperlated iii neither or both of said pole changers areoperated, an alternating current source, a sending distributer, andmeans under the joint control of said distributor and said pole changersto determine the phase of said alternating current. t

in Witness whereof, I hereunto subscribe my name this Qlst day ofNovember A. D., 1919.

Jenn BELL.

